VASCULAR / PROCEDURES

Ultrasound Guided Central Line Pearls & Pitfalls

• Have the patient move their neck sdie to side while looking with the ultrasound. You can choose the degree of rotation with the least overlap between the IJ and the carotid artery. Beware of variable location of vascular structures. Compare sides looking for the larger vein
• Position the ultrasound machine on the same side of the bed you are on with the screen facing you. This helps avoid left-right confusion.
• The vein will collapse with pressure from the probe (unless there is a DVT there in which case choose another site) and will distend with dependent positioning or Valsalva maneuver. If you cannot see the vein, try releasing pressure or having the patient bear down. If you are not sure which is the vein use doppler flow, compression or color flow to assist you or ask for help.
• Touch the probe with your fingertip while watching the screen to double check left from right and be sure you are in tune with which side is which.
• There are two approaches. The transverse approach which is easier to learn and is generally preferred is discussed first.
• Enter the vein close to vertical. This will make it easier to see the needle. Once you are in, or nearly in, adjust to a more shallow angle to avoid a thru-and-thru poke.
• Keep the vein in the center of your screen and the needle at the center of the probe.
• Use a poking or bouncing technique at needle insertion. Motion makes it easier to track your needle.
• Try to track the needle tip, which is the easiest part to see, with your probe by using a fanning motion.
• Unfotunately, metal is difficult to see with ultrasound so you may have to rely as much on motion of tissue planes and downward tenting of the vein wall as you enter it.
• Utilize your colleagues who have more experience than you do, whether it is another emergency physician, or an interventional radiologist
• Pre-load your syringe with lidocaine. When you inject you will notice an obvious white blush. This may help you keep track of the needle tip and has the added bonus of better analgesia. Be aware that venous blood will be much brighter when aspirated into a syringe that still has any lidocaine in it. Also, even a tiny air bubble that is accidentally injected may completely obscure your view of the vein.
• Use the “SCUBA” mnemonic to hit all the key issues in your procedure note. “S” is for Site chosen and reasons why. “C” is for use of Chlorhexidine to prep the skin, as it is more efficacious than Betadine, and also for documenting Consent. “U” is for real time Ultrasound guidance or pre-procedural localization. “B” is for use of wide sterile Barriers, and “A” is for use of an Antibiotic impregnated central line catheter.
• Left-right confusion can lead to missing the mark and traumatic complications.
• Inadvertently injecting an air bubble can completely obliterate your view and force you to abandon the procedure and go to the other side.
• Beware of looking at the needle shaft while the tip is actually elsewhere, such as tickling the carotid artery.
• A longitudinal approach is technically more difficult to master because it is hard to perfectly align the probe and the needle. The benefit of the longitudinal approach is that if you can view the entire needle length you will have more spatial information to guide you.
• You can also use ultrasound guidance to canulate peripheral veins with the cephalic vein and the basilic vein being the primary targets. Use sections of the vein that are straight for at least 3cm and also less than 1cm deep if possible. Don’t use standard 1 inch catheters. Use catheters that are at least 1.75 inches long.

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VASCULAR ULTRASOUND

TRICK: White Blush from injecting lidocaine helps locate needle tip during Central Line insertion under real-time ultrasound guidance. CAUTION: injecting even the tiniest air bubble can destroy your view!

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Normal Femoral Vein under Compression collapses

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Femoral Vein DVT under Compression doesn’t collapse

PEARLS & PITFALLS FOR VENOUS AND ARTERIAL THROMBOEMBOLIC DISEASE

• Know your limitations: Ultrasound may help clarify findings elicited by a thorough history and physical exam.  When used correctly, it can lead to a more rapid diagnosis and/or improve diagnostic accuracy, especially for critical conditions or unstable patients.  If you use ultrasound in your ED, your department should have a quality improvement program set up that is approved by both ED administration and radiology.
• Vein or Artery? 1.) Veins and arteries often run side by side.  You don’t want to confuse them.  A vein tends to be almond shaped and will collapse with pressure from the probe (unless it contains a DVT) as well as distend with dependent positioning. If you cannot see a vein, try releasing probe pressure a bit.  A vein should have non-pulsatile sluggish flow with use of Doppler.
• Vein or Artery? 2.) When viewed in cross section, an artery tends to be circular rather than almond shaped.  Moreover, the walls are thicker and it is therefor relatively non-compressible.  Use of Doppler should show triphasic flow in an unobstructed artery.Vein or Artery? 3.) Often you know which side the artery and vein should be on anatomically.  For example, in the groin, the femoral artery is lateral and the vein medial.  This knowledge however can lead you astray if your probe orientation is reversed. To check orientation, touch the probe with your fingertip while watching the screen.  This should assure that you are not reversed.Identifying a clot.  A clot in the vein tends to have a similar echogenicity to liver.  It also makes the vein non-compressible.  An arterial clot tends to be more hyperechoic (white) like the image shown.  Since arteries tend to be noncompressible, instead check for loss of the normal triphasic arterial Doppler signal.
• Practice Makes Perfect: With bedside ultrasound there is no substitute for experience.  The more ultrasounds you do, the better you will be able to differentiate abnormal from normal, even when you may not be sure exactly what the abnormality is. An image library of normal and abnormal ultrasounds helps immensely and we can help.  Just go to EPMonthly.com, select “Departments”, chose “Real-Time-Readings” and click on the ERPocketBooks.com link under “Ultrasound Library” section on the left side of your screen.

 

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Femoral Arterial Thrombosis

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Femoral Arterial Graft: 2 views

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Normal anatomy of Internal Jugular Vein

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DVT in the Internal Jugular Vein from Central Line

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INTRAVASCULAR VOLUME ASSESSMENT: IVC Measurements by Teresa Wu, MD

• Use the curviliear 3.5 MHz or 5 MHz transducer to obtain the images of deeper structures like the IVC
• The IVC can be found coursing along the inferior edge of the liver, anterior to the spine and on the right side of the pulsatile aorta
• Use the liver as your acoustic window and attempt obtain a longitudinal view of the IVC
• Confirm that the structure you are looking at is indeed a vessel by scanning in two planes and noting an anechoic lumen.  You may also apply Color Doppler and note a constant rumble of color over the target area.
• The aorta will have pulsatile color flow and is non-compressible.  The IVC has non-pulsatile flow and is easily compressed by downward pressure of the ultrasound probe (the “wink” sign)
• The IVC dilates during expiration (IVCe) and collapses during inspiration (IVCi)
• The diameter of the IVC and the amount of inspiratory collapse correlates with central venous pressures
• The mean diameter of the IVC in euvolemia is approximately 1.6 to 1.75 cm
• The proximal portion of the IVC is often wider than the distal portion.  Take 2 to 3 measurements and calculate the mean diameter for assessment.
• Make sure you take measurements of the maximum IVCe and IVCi and the minimum IVCe and IVCi
• As the intravascular volume decreases, the IVCi will become smaller and smaller and then eventually collapse.
• Patients with a mean IVCe diameter of < 0.8-1cm are usually hypovolemic.  Unfortunately, the papers on this topic use the mean of multiple measurements, so there is no simplified, single-measurement cut-off that can be quoted.  Use  0.8-1cm as a guideline
• Obtain serial measurements of the IVC diameter to monitor central blood volume status and response to volume resuscitation
• Every 100 mL of volume changes the IVC diameter by approximately 1 mm
• Note that measurement of the IVC for volume status may be confounded by certain medical conditions that cause IVC dilations, such as cirrhosis, right heart failure, or valvular heart disease

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PROCEDURES: LUMBAR PUNCTURE: Ultrasound Guided Lumbar Puncture Pearls by Teresa Wu, MD

• First described in 1971, an Ultrasound Guided LP can be utilized in patients in whom the landmark approach may be difficult (e.g. patients who are obese, have scoliosis, or those who are unable to create a kyphotic lumbar curve for the procedure).
• Position the patient in a lateral decubitus fetal position
• Use the longest 5 MHz or 7.5 MHz linear probe available
• Start by placing the transducer in a transverse plane over the midline of the patient’s back at the level of the iliac crests. In this view, the spinous processes will cast a dark shadow across the screen. Center the dark shadow in the middle of your ultrasound probe. Use a marker to identify this point as midline on your patient’s back. Extend a short line from cephalad to caudad along this point to clearly distinguish midline.
• Once you’ve demarcated where midline is, rotate the transducer 90? so that it lies parallel to the spine. The spinous processes in this view will appear as hyperechoic(white) curves casting dark shadows farfield to your transducer. Center the transducer over the spinous processes and try to catch two spinous processes on your field. Use a marker to identify the interspinous space. Extend a short line going from the patient’s left to right along this point. Direct your spinal needle towards the point where this interspace line bisects your midline line.
• An LP Guided Ultrasound can be performed in a static or dynamic manner, depending on the number of personnel available to help with the procedure. If you are performing the procedure in a dynamic “real time” manner, remember to use sterile ultrasound gel and prep your ultrasound probe in a sterile fashion. In a static manner the ultrasound is used for localization and marking, then the patient is prepped and draped in the normal sterile fashion and the procedure is performed using pen marks as guides.
• For more advice on ultrasound guided procedures visit ERPocketBooks.com and look for the Ultrasound Image Library.

 

Probe Placement: Longitudinal. (Image courtesy of Teresa Wu, MD)

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SP = Spinous Process. ISP = Intra-Spinous Space

(Image courtesy of Teresa Wu, MD)

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